Which pair of terms best describes the female character as depicted in the excerpt?

We don't have the excerpt, so we cannot really answer your question.
I can help you a bit, however, so if you've read the story, you will know how to answer it yourself.
A flat character is the one who doesn't change at all over the course of a novel, whereas a round character develops and changes his or her characteristics.
A protagonist is the hero of a novel, whereas an antagonist is his "enemy.

The Theme of the text is:

a.Obstacles arise in life, but that doesn’t mean a person should give up on what they want.

Explanation:

In the short story, Chris has gradually accepted his inability to ever walk again, unlike his father Mr. Jim, who finds it really hard to accept his son’s defect after the accident.

Chris, even though hurt by his defect, shows his resilience, as he instantly says yes to a well wisher, Mr. Evans asks him whether he’d be interested in participating in an wheel chair basket ball tournament.  

This shows how Chris was still keen to fulfill his dream of playing basketball, where as for his father, even though he gradually showed his support, he took time to come around to the same feeling.

Hence, “obstacles arise in life, but that doesn’t mean a person should give up on what they want”.